Gasoline composition



April 25, 1967 M. R. BARUSCH ET AL 3,316,071

GASOLINE COMPOSITION Filed Sept. 26, 1958 PARAFFINS & NAPHTHENES M M MA AROMATICS (100%) FIG. 1

OLEF'NS PARAFFINS 8. NAPHTHENES A/VW M MMAA OLEFINS 0.9 \A-HJA AROMATICS (10070) N 0 Hm WU C S K p 5 RU S Y R N E 5% N NE .KL R ERL o EE R T CCE T GL A RLRE 3% v MWGD United States Patent 3,316,071 GASOLINE COMPOSHTION Maurice R. Barusch, Richmond, Wallace L. Richardson, Lafayette, George J. Kautsky, Richmond Annex, and Done] R. Olson, San Pablo, Calif, assignors to Chevron Research Company, a corporation of Delaware Filed Sept. 26, 1958, Ser. No. 765,921 (Filed under Rule 47(a) and 35 U.S.C. 116) 1 Claim. (Cl. 44-69) This invention relates to an improved gasoline com position. More particularly, the invention is concerned with a superior new hydrocarbon fuel of the gasoline boiling range containing lead tetramethyl.

Gasoline compositions of high octane number are commonly required for modern spark ignition internal combustion automobile and aircraft engines. Engines of these types in general use today are designed with high compression ratios for more efficient operation. Since the present trend is toward engines of still higher compression ratios for increased power and improved performance, there is a constant demand for gasoline compositions of even higher octane number.

Improved methods of refining and blending gasoline base stocks, and additives such as lead tetraethyl, have been employed to meet the demands for higher octane number gasoline compositions. However, it has been generally realized that there is at present a limit to the improvement in octane number that can be obtained by such conventional methods and additives. New gasoline base stocks with the combination of different additives are greatly needed, therefore, to avoid present limitations and provide gasoline compositions of high octane number for future use in automobile and aircraft engines.

It has now been found that a superior new gasoline composition of high octane number is provided by a hydrocarbon base fuel boiling in the gasoline boiling range having a clear research octane number of at least 90 and containing at least 20% by volume of aromatic hydrocarbons and less than 30% by volume of olefinic hydrocarbons to which is added at least one milliliter of tetramethyl lead per gallon of hydrocarbon base fuel.

The improved gasoline composition of the invention shows an unexpectedly high octane number compared to previously known combinations of hydrocarbon base fuels and additives. The particular hydrocarbon base fuel, together with the specified lead tetramethyl in accordance with the invention, has an octane number which is substantially higher than similar base fuels employing the conventional lead tetraethyl additive in the same lead content. This is surprising since it has been generaly accepted heretofore that lead tetramethyl is distinctly less efficient than lead tetraethyl and other lead alkyls with respect to octane number improvement.

Prior to the present invention, gasoline compositions depending on conventional hydrocarbon base fuels to which lead tetraethyl had been added for octane number improvement were found to reach very soon a practical maximum in octane number at which the addition of further quantities of lead tetraethyl would provide very little or no benefit. The gasoline composition of the invention, on the other hand, is improved markedly by additional quantities of lead tetramethyl at octane numbers considerably above the aforementioned practical maximum encountered in the use of lead tetraethyl in previously known gasoline compositions. This means that a higher octane number is obtained with lead tetramethyl in the gasoline compositions of the invention than can be obtained with lead tetraethyl.

The hydrocarbon base fuel of the composition, according to the invention, is prepared by conventional refining and blending processes. It normally contains straight-chain paraffins, branched-chain parafiins, olefins, aromatics and naphthenes. Since straight-chain paraflins have a tendency to adversely affect octane number, the content of such hydrocarbons is ordinarily low.

As already mentioned, the base fuel is a hydrocarbon fuel boiling in the gasoline boiling range. Generally described, such fuels have an ASTM (D-86) distillation with an initial boiling point of about 100 F. and a final boiling point of about 425 F. The unleaded base fuel has a Research octane number of at least 90 as determined by the accepted CFR engine test method. The base fuel contains at least 20% by volume of aromatic hydrocarbons. Less than 30% by volume of olefinic hydrocarbons are present in the fuel. The total paraffin and naphthene hydrocarbon content of the fuel may be as much as by volume. For best over-all engine performance, fuels containing in the range of 20 to 60% by volume of paraffinic and naphthenic hydrocarbons are preferred for volatility and other desirable gasoline characteristics.

The lead tetramethyl is employed in the gasoline composition of the invention in amounts of at least 1.0 milliliter per gallon of base fuel. In these amounts, the lead tetramethyl in combination with the base fuel produces an octane number improvement greater than that which can be obtained with equivalent molar amounts of lead tetraethyl in the same base fuel. For practical purposes, not more than about 4 milliliters of lead tetramethyl per gallon is ordinarily used in the compositions.

If desired, other octane-improving additives may be employed in addition to lead tetramethyl. These include other lead compounds such as lead tetraethyl, carbonyl derivatives of iron and cyclopentadienyl derivatives of metals such as manganese or iron. Other gasoline additives, such as scavengers like ethylene chloride or bromide, oxidation inhibitors, corrosion inhibitors, surface ignition suppressants like phosphorus compounds, detergents, and the like may be present.

In further illustration of the superior new gasoline composition of the invention, numerous compositions and tests thereon are given in the following examples. These tests show the improved effect of the combination of the particular hydrocarbon base fuel with at least 1.0 milliliter of lead tetramethyl as compared with other different hydrocarbon base fuels containing either lead tetramethyl or lead tetraethyl. These tests also show the improved effect of the combination of the particular hydrocarbon base fuel with at least 1.0 milliliter of lead tetramethyl compared with similar hydrocarbon fuels containing either lead tetraethyl in any equivalent amount or lead tetramethyl in amounts less than the aforementioned 1.0 milliliter per gallon.

The following table is a summary of the pertinent data of the examples. The type of compositions of the hydrocarbon base fuel is shown with respect to the percent by volume of the paraffins and naphthenes, olefins and aromatics. The clear octane number of the base fuel is also given. This octane number, as already mentioned, is the accepted Research octane number which is usually employed in designating a given gasoline. This method is 3 described as Research Method D-908 in ASTM Manual of Engine Test Methods for Rating Fuels.

The table also shows the effect on octane number by the addition of certain amounts of lead tetramethyl, as compared to lead tetraethyl. The octane number in this comparison is based on the Motor Method D357 of the ASTM Manual of Engine Test Methods for Rating Fuels. This method, which is more stringent than the Research Method, illustrates more accurately the desirable qualities of the improved gasoline composition of the invention.

The effect of the improved gasoline composition of the invention is also shown by the road octane ratings in the following table. These ratings are determined by chassis dynamometer tests in accordance with the accepted Modified Uniontown Test Procedure. In these determinations, eight different makes of automobiles of recent manufacture (1956-195 8) were employed, some of which were modified to provide increased compression ratios. At standard timing, the octane requirement of these automobiles ranges from about 94 to 102 octane numbers. The compression ratios vary from about 8.5 to 1 to as high as about 12 to 1.

In the table, the effect of lead tetramethyl (LTM) compared with lead tetraethyl (LTE) is based on gasoline compositions containing an equal lead concentration. That is to say that 2.06 milliliters per gallon of lead tetramethyl is compared with 3.00 milliliters per gallon lead tetraethyl because of the difference in densities and molecular weights of the compounds. The Improvement is the difference in the octane number obtained with lead tetramethyl less the octane number obtained with the equivalent amount of lead tetraethyl.

similar compositions containing lesser amounts of aromatic hydrocarbons. The above examples also show that when the olefinic hydrocarbon content of the base fuel exceeds 30% by volume, the octane number of the fuel containing lead tetramethyl is adversely affected.

The improvement in octane number obtained with the gasoline composition containing lead tetramethyl, in accordance with the present invention, is also effectively illustrated by the trilinear charts of the accompanying drawings. The charts define the areas of the preferred type of compositions based on the Improvement or difference between the Motor Method octane numbers of certain hydrocarbon base fuel compositions containing 2.06 milliliters of lead tetramethyl and similar compositions containing 3.00 milliliters of lead tetraethyl. The numbers on the points in the charts represent the Improvement or difference in Motor octane number.

In the charts it is shown that the combination of the particular hydrocarbon base fuel and lead tetramethyl of the invention, as previously described, is definitely superior in motor octane number compared to other hydrocarbon base fuels. The chart of FIGURE 1 shows that there is an enhancement of octane number with the use of lead tetramethyl instead of lead tetraethyl in the present compositions within a certain area bounded by the straight lines connecting A, B, C and D, whereas there is a depreciation in octane number when the same substitution is made with other hydrocarbon compositions outside that area. The better improvements in octane number are obtained with the more particular and preferred hydrocarbon compositions as illustrated by the reduced area bounded by the straight lines connecting A, B, C, D and E in the chart of FIGURE 2 of the drawing.

Hydrocarbon Composition, Percent Motor Octane Road Octane by Volume Ex. Research Improve- Improve- No. No. Octane LTM LTE merit LTM LTE merit of Paraflins Unleaded Cars an Olefins Aromatics Naphthenes M1. N0. M1. N0. M1. N0. M1. N0.

51 25 24 93. 3 2.06 87. 6 3.0 87.0 0.6 2. 06 96. 7 3.0 96.0 0. 7 6 44 30 26 94. 5 2.06 87. 1 3. 86.6 0.5 2.06 97.6 3.0 97.0 0. 6 6 29 29 42 98. 3 2.06 88. 3.0 87. 4 1.1 2.06 98. 5 3.0 97.6 0.9 6 47 33 94. 1 2.06 89.0 3.0 88. 3 0.7 2.06 98. 2 3.0 97.3 0. 9 3 38 37 97. 2 2.06 89.0 3. 0 88. 2 0.8 2.06 99. 2 3.0 98. 2 1. 0 6 53 11 36 97. 2 2. 06 92. 5 3.0 90.7 1. 8 2.06 100.2 3.0 98.8 1. 4 3 54 Trace 46 98. l 2. 06 96. 5 3.0 95.2 1. 3 2.06 105. 8 3.0 104.0 1. 8 3 76 0 24 97. 4 2.06 100.4 3. 0 100. 1 0. 3 2. 06 107. 0 3.0 106. 5 0. 5 3 76 0 24 97. 4 0.69 95. 2 1. 0 95. 2 0.0 0.69 103. 2 1. 0 104.0 -O. 8 1 44 26 94. 5 0.69 84. 8 1. 0 84. 2 0.6 0.69 97.4 1. 0 98. 9 1. 5 1 54 1 98. 6 0.69 92. 9 1. 0 92.4 0. 5 0.69 104. 8 1. 0 105.1 0. 3 1 41 16 43 95. 6 0.69 86. 2 1. 0 85. 2 1. 0 0.69 95. 1 1. 0 95. 2 0. 1 5 41 16 43 95.6 2.06 88. 6 3.0 87.8 0.8 2.06 98.0 3.0 96. 8 1. 2 6 41 16 43 95. 6 4.12 90.8 6.0 90.1 0.7 4.12 99. 6 6.0 98. 2 1.4 3 100 0 0 91. 3 2.06 103. 6 3.0 107.3 3. 7

The examples summarized in the above table show that the improved gasoline composition of the 1nvent1on con- We claim:

taining lead tetramethyl is decidedly better on the basis of octane number rating than comparable gasoline compositions of the type known heretofore. The hydrocarbon base fuels having a clear (unleaded) octane number of at least 90 in combination with at least 1.0 milliliter of lead tetramethyl provide a gasoline composition of much greater Road octane number improvement than can be obtained with similar hydrocarbon base fuels containing either lead tetraethyl or less than 1.0 milliliter of lead tetramethyl. The compositions having at least 2 0% by volume of aromatic hydrocarbons are greatly superior to A hydrocarbon base fuel, boiling in the gasoline boiling range, adapted for use in spark ignition internal combustion engines, having a clear Research octane number of at least 90, said fuel being characterized in that the hydrocarbon composition thereof lies within the 4-sided figure of FIGURE 1, which 4-sided figure is identified by the fact that its area lies within the straight lines connecting A, B, C, and D; said fuel containing from about one to about four milliliters of lead tetramethyl per gallon, said fuel having 2. Motor Method octane number and an average Road octane number greater than the corresponding References Cited by the Examiner UNITED STATES PATENTS Midgley 446'9 Fischer et a1. 44 69 Smyers et a]. 44 69 Risk 208-47 Ross et a1. 44-80 Pevere 4480 Morrow 4469 Bartleson 4469 Lichtenfels 4480 Hin-karnp et a1 4469 De Witt 4469 Lyben 44 69 Housarn et a1 20817 6 2,897,071 7/19'59 Gilbert 4469 2,897,072 7/1959 Hooper et al. 208l7 2,913,413 11/1959 Brown 4469 OTHER REFERENCES Aviation Gasoline Manufacture, by Van Winkle, First Ed. 1944, McGraw-H-ill Book Co. Inc., pages 197-204.

Conversion of Petroleum, by Sachanen, 1940, Reinhold Pub. Co., pages 301-303.

Improved Motor Fuels Through Selective Blending, 10 by Wagner et al., paper presented before 22nd Annual Meeting of the American Petroleum Institute, Nov. 7, 1941, pages 6 to 11 of 19 pages.

15 DANIEL E. WYMAN, Primary Examiner.

JULIUS GREENWALD, Examiner. Y. H. SMITH, Assistant Examiner. 

